Magnetic device and memory device

ABSTRACT

According to one embodiment, a magnetic device includes: a first magnetic material provided above a substrate; a second magnetic material provided between the substrate and the first magnetic material; a nonmagnetic material provided between the first magnetic material and the second magnetic material; a first layer provided between the substrate and the second magnetic material and including an amorphous layer; and a second layer provided between the amorphous layer and the second magnetic material and including a crystal layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2019-049562, filed Mar. 18, 2019, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic device and amemory device.

BACKGROUND

In order to improve the characteristics of magnetoresistive effectelements, the study and development of structures and structural membersof the elements have been promoted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a basic example of a magnetic deviceaccording to an embodiment.

FIG. 2 is a diagram illustrating an example of a configuration of themagnetic device according to the embodiment.

FIGS. 3, 4, 5, 6, 7, 8 and 9 are graphs illustrating the characteristicsof the magnetic device according to the embodiment.

FIG. 10 is a diagram illustrating a modification to the magnetic deviceaccording to the embodiment.

FIGS. 11, 12 and 13 are diagrams illustrating an application example ofthe magnetic device according to the embodiment.

DETAILED DESCRIPTION Embodiment

An embodiment will be described in detail below with reference to FIGS.1 through 13. In the following descriptions, the elements having thesame function and configuration are denoted by the same referencenumeral or sign.

If the elements denoted by reference signs with numerals or letters attheir ends (e.g. word lines, bit lines, and various voltages andsignals) need not be distinguished from one another, the numerals orletters will be excluded.

In general, according to one embodiment, a magnetic device includes: afirst magnetic material provided above a substrate; a second magneticmaterial provided between the substrate and the first magnetic material;a nonmagnetic material provided between the first magnetic material andthe second magnetic material; a first layer provided between thesubstrate and the second magnetic material and including an amorphouslayer; and a second layer provided between the amorphous layer and thesecond magnetic material and including a crystal layer.

(1) Embodiment

A magnetic device according to an embodiment and a method ofmanufacturing the magnetic device will be described with reference toFIGS. 1 through 9.

(a) Basic Example

A basic example of the magnetic device according to the embodiment willbe described with reference to FIG. 1.

FIG. 1 is a schematic sectional view showing a basic configuration of amagnetoresistive effect element 400A of the present embodiment.

As shown in FIG. 1, the magnetoresistive effect element 400A includestwo magnetic materials 11A and 12A, a nonmagnetic material 13A and anunderlying layer (nonmagnetic material) 19A. Note that the nonmagneticmaterial may be referred to as the nonmagnetic material layer, and themagnetic material may be referred to as the magnetic material layer.

The magnetic materials 11A and 12A are provided above a substrate 80 ina direction perpendicular to the surface of the substrate 80 (which isdefined as a Z direction here).

The magnetic material 11A is provided between the magnetic material 12Aand the substrate 80. The magnetic material 11A includes at least onemagnetic layer 111A.

The magnetic material 11A includes, for example, two magnetic layers111A and 115A and a nonmagnetic layer 116A. The magnetic layer 111A isprovided above the magnetic layer 115A in the Z direction. Thenonmagnetic layer 116A is provided between two magnetic layers 111A and115A. The nonmagnetic layer 116A is a metal layer.

As described above, the magnetic material 11A is a stack including aplurality of layers 111A, 115A and 116A stacked in the Z direction.

For example, the magnetic material 11A has a synthetic antiferromagnetic(SAF) structure. The two magnetic layers 111A and 115A of the magneticmaterial 11A are antiferromagnetically bonded to each other with thenonmagnetic metal layer 116A therebetween. In the SAF structure, thedirection of magnetization of the magnetic layer 111A is opposite tothat of magnetization of the magnetic layer 115A.

Hereinafter, the magnetic material 11A will also be referred to as anSAF structure (or an SAF layer) 11A.

The nonmagnetic material 13A is provided between the magnetic material11A and the magnetic material 12A.

The underlying layer 19A is provided between the SAF structure 11A andthe substrate 80.

The underlying layer 19A is a stack. The underlying Layer 19A includes aplurality of layers 190A and 199A. The layer 199A is provided betweenthe magnetic material 11A and the substrate 80. The layer 190A isprovided between the magnetic material 11A and the layer 199A. Theunderlying layer 19A is thus a stack including a plurality of layersstacked in the Z direction.

The underlying layer 19A functions as a layer for improving thecharacteristics of the magnetic material 11A.

One or more layers (members) may be provided between the substrate 80and the magnetic material 11A.

The magnetic device of the present embodiment corresponds to themagnetoresistive effect element 400A. The magnetoresistive effectelement 400A can take a plurality of resistance states (amagnetoresistance value and a resistance value) in accordance with therelative magnetization alignment of the two magnetic materials 11A and12A.

In the present embodiment, the layer 199A of the underlying layer 19A isa layer including an amorphous layer (hereinafter referred to as anamorphous layer).

In the present embodiment, the layer 190A of the underlying layer 19A isa layer including a crystal layer (hereinafter referred to as a crystallayer). The crystal layer 190A has a single-layer structure or amulti-layer structure.

The amorphous layer 199A is provided on the undersurface of the crystallayer 190A in the Z direction. The amorphous layer 199A prevents thecrystal properties (e.g. crystal information and defect information) ofa layer (e.g. the substrate 80 and a conductive layer) under theamorphous layer 199A from being propagated (transcribed) to a layer(e.g. the crystal layer 190A and the magnetic material 11A) above theamorphous layer 199A. The crystal layer 190A can promote the crystalgrowth of the magnetic material 11A.

Since the amorphous layer 199A prevents the crystal properties of alayer under the amorphous layer 199A from being propagated, the crystalof the magnetic material 11A grows, generally depending upon the crystalproperties of the crystal layer 190A. In the present embodiment,therefore, the crystal of the magnetic material 11A is improved in itsuniformity.

In addition, the amorphous layer 199A has relatively high flatness.Accordingly, the crystal layer 190A, magnetic materials 11A and 12A andnonmagnetic material 13A, which are provided on and above the amorphouslayer 199A, are improved in their flatness.

As a result, the magnetic properties of the magnetic materials 11A and12A are improved in the magnetoresistive effect element of the presentembodiment.

Thus, the characteristics of the magnetoresistive effect element(magnetic device) of the present embodiment are improved.

(h) Configuration Example

The configuration of the magnetoresistive effect element (MTJ element)400 of the present embodiment will be described with reference to FIG.2.

FIG. 2 is a schematic sectional view showing a configuration example ofthe magnetoresistive effect element according to the present embodiment.For clarification, a protection film and an interlayer insulating film,which cover the element, are excluded from FIG. 2.

As illustrated in FIG. 2, the magnetoresistive effect element 400 of thepresent embodiment has a rectangular sectional shape. However, themagnetoresistive effect element 400 may have a trapezoidal sectionalshape of the base shape. For example, a plane shape (a shape in a viewfrom Z-direction) of the MTJ element 400 may be circular, elliptical orquadrangular (e.g. square and rectangular). When the MTJ element isrectangular, the corners of the magnetic layer may be rounded.

The magnetoresistive effect element 400 of the present embodimentincludes stacks 10 and 19 and two electrodes 30 and 31. The stack 10 isprovided between the two electrodes 30 and 31. The stack 19 is providedbetween the stack 10 and the electrode 30.

The electrode 30 is provided at one end of the magnetoresistive effectelement 400 in the Z direction. The electrode 31 is provided at theother end thereof in the Z direction. The electrode 31 is provided abovethe electrode 30 in the Z direction. Hereinafter, the electrode 30 willbe referred to as a lower electrode 30 and the electrode 31 will bereferred to as an upper electrode 31.

The materials of the electrodes 30 and 31 include at least one ofRuthenium (Ru), tungsten (W), tantalum (Ta), tantalum nitride (TaN),titanium (Ti), titanium nitride (TiN) and the like.

Incidentally, each of the electrodes 30 and 31 may have a single-layerstructure or a multilayer structure.

The stack 10 includes at least two magnetic materials 11 and 12 and anonmagnetic material 13.

The magnetic material 11 is provided between the lower electrode 30 andthe nonmagnetic material 13. The magnetic material 12 is providedbetween the upper electrode 31 and the nonmagnetic material 13. Thenonmagnetic material 13 is provided between the two magnetic materials11 and 12. Between the two magnetic materials 11 and 12, a magnetictunnel junction (MTJ) is formed through the nonmagnetic material 13.

Hereinafter, the magnetoresistive effect element including an MTJ willbe referred to as an MTJ element. The nonmagnetic material 13 will bereferred to as a tunnel barrier layer 13. The tunnel barrier layer 13is, for example, an insulating film including magnesium oxide (MgO).

The magnetic material 12 has magnetization. The direction of themagnetization of the magnetic material 12 is variable. Hereinafter, themagnetic material 12 having a variable magnetization direction will bereferred to as a storage layer 12. The storage layer 12 may also bereferred to as a free layer, a magnetization variable layer and amagnetization free layer.

The storage layer 12 is provided between the electrode 31 and the tunnelbarrier layer 13. The storage layer 12 is in contact with the electrode31. However, one or more layers (referred to as a cap layer hereinafter)may be provided between the electrode 31 and the storage layer 12. Thecap layer may include, for example, a magnesium oxide layer.

The storage layer 12 includes cobalt iron boron (CoFeB), iron boride(FeB) or the like.

The magnetic material 11 is a stack having an SAF structure. Themagnetic material 11 with the SAF structure includes two magnetic layers111 and 115 and a nonmagnetic layer 116. The nonmagnetic layer 116 is ametal layer. The nonmagnetic layer 116 is, for example, a ruthenium film(Ru film).

Each of the magnetic layers 111 and 115 has magnetization. The directionof the magnetization of the magnetic layer 115 is opposite to that ofthe magnetization of the magnetic layer 111. The two magnetic layers 111and 115 are bonded anti-ferromagnetically through the metal layer 116.Thus, the magnetizations of the two magnetic layers 111 and 115 arefixed to each other.

Of the two magnetic layers 111 and 115 of the magnetic material 11 withthe SAF structure, the magnetic layer 111 closer to the upper electrode31 will be referred to as a reference layer 111. The reference layer 111may also be referred to as a pin layer, a pinned layer, a magnetizationfixed layer or a magnetization invariable layer. Of the two magneticlayers 111 and 115, the magnetic layer 115 closer to the lower electrode30 will be referred to as a shift cancellation layer 115. Note that themagnetic layer 11 with the SAF structure may also be referred to as areference layer.

The shift cancellation layer 115 reduces a stray magnetic field of thereference layer 111. This suppresses an adverse effect on themagnetization of the storage layer 12 due to the stray magnetic field ofthe reference layer 111 (e.g. a magnetic field shift).

For example, the reference layer 111 includes cobalt iron boron (CoFeB)or iron boride (FeB). The reference layer 111 may also include cobaltplatinum (Copt), cobalt nickel (CoNi) or cobalt palladium (CoPd). Forexample, the reference layer 111 is an alloy film or a multi-layer film(e.g. an artificial lattice film) using these materials.

For example, the material of the shift cancellation layer 115 is thesame as that of the reference layer 111.

The direction of magnetization of the reference layer 111 is invariable(fixed) and so is the direction of magnetization of the shiftcancellation layer 115. The fact that the direction of magnetization ofeach of the reference layer 111 and shift cancellation layer 115 is“invariable” or “fixed” means that when the MTJ element 400 is suppliedwith current or voltage for reversing the direction of magnetization ofthe storage layer 12, the direction of magnetization of each of thereference layer 111 and shift cancellation layer 115 does not changebefore and after the supply of the current or voltage. As the directionof magnetization of each of the reference layer 111 and shiftcancellation layer 115 is invariable, the magnetization switchingthreshold value of the storage layer 12, that of the reference layer 111and that of the shift cancellation layer 115 are each controlled. If thestorage layer and the reference layer (and the shift cancellation layer)are formed of the same material, the reference layer 111 is made thickerthan the storage layer 12 to control the magnetization switchingthreshold value.

For example, the storage layer 12, the reference layer 111 and the shiftcancellation layer 115 each have perpendicular magnetic anisotropy. Thedirection of magnetization of each of the storage layer 12, referencelayer 111 and shift cancellation layer 115 is substantiallyperpendicular to the layer surface (film surface) of the layer 12 (andlayers 111 and 115). The direction of magnetization of each of themagnetic layers 12, 111 and 115 (the direction of easy axis ofmagnetization) is substantially parallel to the direction in which themagnetic layers 12, 111 and 115 are stacked.

The magnetization of storage layer 12 directs toward one of the lowerelectrode 30 and the upper electrode 31. The fixed magnetization of thereference layer 111 is set toward one of the lower electrode 30 and theupper electrode 31 by the SAF.

The resistance state (resistance value) of the MTJ element 400 varieswith the relative relationship (magnetization alignment) between thedirection of magnetization of the storage layer 12 and that ofmagnetization of the reference layer 111.

When the direction of magnetization of the storage layer 12 is the sameas that of magnetization of the reference layer 111 (when themagnetization alignment of the MTJ element 400 is parallel), the MTJelement 400 has a first resistance value R1. When the direction ofmagnetization of the storage layer 12 is different from that ofmagnetization of the reference layer 111 (when the magnetizationalignment of the MTJ element 400 is antiparallel), the MTJ element 400has a second resistance value R2 that is higher than the firstresistance value R1.

In the present embodiment, the parallel alignment state of the MTJelement 400 will also be referred to as a P state and the antiparallelalignment state thereof will also be referred to as an AP state.

For example, when the direction of magnetization of the storage layer isswitched by spin torque transfer (STT), write current is supplied to theMTJ element 400.

The change in magnetization alignment of the MTJ element 400 from the APstate to the P state or the change therein from the P state to the APstate is controlled according to whether write current flows from thestorage layer 12 to the reference layer 111 or from the reference layer111 to the storage layer 12. The value of the write current is smallerthan the magnetization switching threshold value of the reference layer111 and is set not smaller than the magnetization switching thresholdvalue of the storage layer 12. Thus, spin torque that contributes to themagnetization switching of the storage layer 12 is applied to thestorage layer 12.

When the magnetization alignment of the MTJ Element 400 is changed fromthe AP state to the P state, the spin torque of spin (electron) whose adirection is the same as a magnetization direction of the referencelayer 111, is applied to the magnetization of the storage layer 12. Whenthe direction of magnetization of the storage layer 12 is opposite tothat of magnetization of the reference layer 111, the direction ofmagnetization of the storage layer 12 is changed to the same directionas that of magnetization of the reference layer 111 by the applied spintorque.

As a result, the magnetization alignment of the MTJ element 400 is setin the P state. Incidentally, when the spin torque of spin whose adirection is the same as a magnetization direction of the referencelayer 111 is applied the storage layer 12 of the MTJ element 400 in theP state, the direction of magnetization of the storage layer 12 is notchanged. The MTJ element 400 is therefore maintained in the P state.

When the magnetization alignment of the MTJ Element 400 is changed fromthe P state to the AP state, the spin torque of spin whose a directionis opposite to a magnetization direction of the reference layer 111 isapplied to the magnetization of the storage layer 12. When the directionof magnetization of the storage layer 12 is the same as that ofmagnetization of the reference layer 111, the direction of magnetizationof the storage layer 12 is changed to a direction opposite to that ofmagnetization of the reference layer 111 by the applied spin torque.

As a result, the magnetization alignment of the MTJ element 400 is setin the AP state. Incidentally, when the spin torque of spin whose adirection is opposite to a magnetization direction of the referencelayer 111 is applied the storage layer 12 of the MTJ element 400 in theAP state, the direction of magnetization of the storage layer 12 is notchanged. The MTJ element 400 is therefore maintained in the AP state.

When the resistance value of the MTJ element 400 is discriminated, readcurrent is supplied to the MTJ element 400. The current value of theread current is set to a value that is smaller than the magnetizationswitching threshold value of the storage layer 12. Based upon themagnitude of the value (e.g. a current value and a voltage value) outputfrom the MTJ element 400 that is supplied with the read current, theresistance value (magnetization alignment state) of the MTJ element 400is equivalently discriminated.

In the MTJ element 400 of the present embodiment, the stack 19 isprovided between the SAF-structure magnetic material 11 and the lowerelectrode 30. The stack. 19 is a nonmagnetic material. Hereinafter, thestack 19 will be referred to as an underlying layer 19.

The underlying layer 19 is a stack including a first layer 191 and asecond layer 192. The first layer 191 and second layer 192 are stackedin the Z direction.

The first layer 191 is provided between the lower electrode 30 and thesecond layer 192. The second layer 192 is provided between the magneticmaterial 11 and the first layer 191. The second layer 192 is in directcontact with, for example, the shift cancellation layer 115.

The first and second layers 191 and 192 are, for example, crystallayers. The first and second layers 191 and 192 function as bufferlayers for crystal growth of the magnetic material 11 (magnetic layer115) at the time of formation of the magnetic material 11. Hereinafter,the first layer 191 and the second layer 192 will be referred to as afirst buffer layer and a second buffer layer. The second buffer layer192 is provided above the first buffer layer 191 in the Z direction. Astack-structure buffer layer (layer 190 in FIG. 1) is formed by thelayers 191 and 192.

For example, the first buffer layer 191 improves the crystallinity(orientation) of the second buffer layer 192. The second buffer layer192 improves the crystallinity (orientation) of the magnetic layer onthe second buffer layer 192.

The second buffer layer (crystal layer) 192 preferably has a crystalstructure similar to the crystal structure of a layer (here, the shiftcancellation layer 115) that is in contact with the second buffer layer192. When, for example, a material having a crystal orientation (crystalstructure) of fcc (111) and/or hcp (0002) is used for the shiftcancellation layer 115, the second buffer layer 192 preferably has, forexample, a crystal orientation of fcc (111) and/or hcp (0002).

For example, the material of the first buffer layer 191 is tantalum(Ta). For example, the material of the second buffer layer 192 isselected from among ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium(Os), iridium (Ir), platinum (Pt) and the like. In this case, forexample, a CoPt-based material is used for the material of the shiftcancellation layer 115 (and the reference layer 111).

Neither the material of the first buffer layer 191 nor the material ofthe second buffer layer 192 is limited to the above example. Thecombination of materials of the first buffer layer 191, second bufferlayer 192 and shift cancellation layer 115 is preferably selectedappropriately in consideration of, e.g. the thermal expansioncoefficient, lattice constant and crystal structure of the materials(layers).

For example, the underlying layer 19 includes a layer 199 other than thefirst buffer layer 191 and the second buffer layer 192.

The layer (also referred to as a spacer layer hereinafter) 199 isprovided between the lower electrode 30 and the first buffer layer 191.The layer 199 is, for example, an amorphous layer. The layer 199 ispreferably a metal layer or a compound layer having conductivity (e.g.,a boride layer or a nitride layer). The material of the layer 199 is,for example, hafnium boride (HfB).

The thickness of the amorphous layer 199 is not less than the total ofthe thickness of the buffer layer 191 and that of the buffer layer 192.The thickness of the amorphous layer 199 and those of the buffer layers191 and 192 are dimensions in a direction perpendicular to the surfaceof the substrate 80 (Z direction).

Note that the spacer layer may be treated as part of the lower electrode30.

In the present embodiment, the underlying layer 19 including anamorphous layer and a buffer layer (crystal layer) improves the magneticproperties of the magnetic layer included in the SAF structure.

As a result, the characteristics of the MTJ element 400 of the presentembodiment is improved.

(c) Characteristics

The characteristics of the MTJ element according to the presentembodiment will be described with reference to FIGS. 3 through 9.

FIG. 3 is a graph showing an example of the characteristics of theunderlying layer in the MTJ element of the present embodiment.

In the graph of FIG. 3, the horizontal axis represents to a magneticfield (H[kOe]) and the vertical axis represents Ms×t (product ofsaturation magnetization and film thickness) ([emu/cm²]).

FIG. 3 shows the magnetic properties of an Ru/Ta/HfB layer as an exampleof the present embodiment. FIG. 3 also shows the magnetic properties ofan Ru/Ta layer as a comparative example of the Ru/Ta/HfB layer. In thefollowing, the case where a stack (multi-layer film) including a layer“A” and a layer “B” is represented by “A/B” means that the layer “A” isstacked on the top surface of the layer “B.”

In the Ru/Ta/HfB layer, the thickness of the Ru layer is 2.0 nm, thethickness of the Ta layer is 1.0 nm and the thickness of the HfB layeris 2.0 nm. In the Ru/Ta layer of the comparative example, the thicknessof the Ru layer is 2.0 nm and the thickness of the Ta layer is 2.0 nm.

As shown in FIG. 3, a tendency to the magnetic properties of theRu/Ta/HfB layer exhibits substantially the same as a tendency to themagnetic properties of the Ru/Ta layer, regardless of the presence orabsence of HfB.

When an MTJ element including a shift cancellation layer is formed usingthe underlying layer of the Ru/Ta/HfB layer, the HfB layer of amorphoushaving no crystal properties (crystal information) prevents the crystalproperties of the substrate from being reflected in (transferred to) thecrystal properties of the magnetic layer on the underlying layer.Furthermore, a relatively flat underlying layer is formed by theamorphous layer.

The above improves the crystal properties of the magnetic layer that isin contact with the underlying layer and the characteristics of a stackincluding the magnetic layer (e.g. a magnetic tunnel junction).

For example, in the MTJ element having the structure shown in FIG. 2,the deterioration of the characteristics of the shift cancellation layerdue to the crystal properties of the substrate is suppressed.Accordingly, the characteristics of the shift cancellation layer areimproved, as are the characteristics of the SAF structure of the shiftcancellation layer and the reference layer.

As a result, the characteristics (e.g. reliability and/or TMRcharacteristics) of the MTJ element of the present embodiment areimproved.

FIGS. 4 through 6 show the relationship between variations of thicknessof the buffer layer of the underlying layer and the characteristics ofthe magnetic material and magnetoresistive effect element.

In FIGS. 4 through 6, as an example of the underlying layer of thepresent embodiment, a Pt/Ta layer is used in the buffer layer and an HfBlayer is used in the amorphous layer. As another example of theunderlying layer, a Ru/Ta layer is used in the buffer layer and an HfBlayer is used in the amorphous layer. The amorphous layer is providedbetween the substrate and the buffer layer.

FIGS. 4 through 6 show an underlying layer (Ru/Ta layer) having a stackstructure of Ru and Ta layers as a comparative value. In the Ru/Ta layerof the comparative value, the Ru layer has a thickness of 2 nm and theTa layer also has a thickness of 2 nm.

As shown in FIGS. 4 through 6, the thickness×of the buffer layer variesin the range from 0 nm to 2 nm.

FIG. 4 is a graph showing an example of the magnetic characteristics ofthe magnetic material on the underlying layer in the present embodiment.

In the graph of FIG. 4, the horizontal axis represents the thickness×ofthe buffer layer and the vertical axis represents the surface roughness(surface morphology) Rq of the magnetic layer on the buffer layer. Notethat the surface roughness (surface morphology) Rq is an indexrepresenting the irregularities of the surface of the layer.

As shown in FIG. 4, the thickness×of the buffer layer varies in therange from 0 nm to 2 nm. Hereinafter, the buffer layer of a Pt layerwill be referred to as a Pt buffer layer and the buffer layer of a Rulayer will be referred to as a Ru buffer layer.

As shown in FIG. 4, in the stack structure of the amorphous layer andthe Pt buffer layer (Pt/Ta/HfB layer), the surface roughness (Rq) of themagnetic material (e.g. SAF structure) on the Pt buffer layer is smallerthan a comparative value V1 if the thickness of the Pt buffer layer is 2nm or less.

Similarly, in the stack structure of the amorphous layer and the Rubuffer layer (Ru/Ta/HfB layer), the surface roughness (Rq) of themagnetic material on the Ru buffer layer is smaller than the comparativevalue V1 if the thickness of the Ru buffer layer is 2 nm or less.

FIG. 5 is a graph showing an example of the magnetic characteristics ofthe magnetic material on the underlying layer in the present embodiment.

In the graph of FIG. 5, the horizontal axis represents thethickness×[nm] of the buffer layer (Ru layer or Pt layer) and thevertical axis represents the strength Hex [Oe] of an exchange couplingmagnetic field of the magnetic material (e.g. SAF structure) on theunderlying layer.

As shown in FIG. 5, the thickness×of the buffer layer varies in therange from 0 nm to 2 nm.

As shown in FIG. 5, when a Pt layer is used in the buffer layer, thestrength Hex of the exchange coupling magnetic field of the magneticmaterial on the Pt buffer layer can be not smaller than a comparativevalue V2 if the thickness of the Pt buffer layer is 1 nm or more.

When a Ru layer is used in the buffer layer, the strength Hex of theexchange coupling magnetic field of the magnetic material on the Rubuffer layer can be almost equal to the comparative value V2 if thethickness of the Ru buffer layer is 2 nm or more.

FIG. 6 is a graph showing an example of the characteristics of themagnetoresistive effect element on the underlying layer in the presentembodiment.

In the graph of FIG. 6, the horizontal axis represents thethickness×[nm] of the buffer layer (Ru layer or Pt layer) and thevertical axis represents the tunnel magnetic resistance ratio (TMRratio) of the magnetoresistive effect element (MTJ element).

As shown in FIG. 6, the thickness×of the buffer layer varies in therange from 0 nm to 2 nm.

As shown in FIG. 6, when the Pt layer is used as a buffer layer, thevalue of the TMR ratio of the magnetoresistive effect element is largerthan a comparative value V3.

When the Ru layer is used as a buffer layer, the TMR ratio of themagnetoresistive effect element is maintained at almost the comparativevalue V3.

Therefore, when the Pt layer is used in the buffer layer of theunderlying layer, if the thickness of the Pt buffer layer is 1 nm ormore and 2 nm or less, the magnetoresistive effect element on the bufferlayer can be improved in its flatness, magnetic properties and TMRratio.

FIGS. 7 through 9 show the relationship between variations of thicknessof the buffer layer of the underlying layer and the characteristics ofthe magnetic material and magnetoresistive effect element.

In FIGS. 7 through 9, as in the example of FIGS. 4 through 6, a Pt/Talayer is used in the buffer layer and an HfB layer is used in theamorphous layer as an example of the underlying layer. The Ta layer isprovided between the HfB layer and the Pt layer.

Like FIGS. 4 through 6, FIGS. 7 through 9 show a characteristic value ofan underlying layer of a Ru/Ta layer as a comparative value. In theunderlying layer of the comparative value, the Ru layer has a thicknessof 2 nm and the Ta layer also has a thickness of 2 nm.

As shown in FIGS. 7 through 9, the thickness×of the buffer layer variesin the range from 0 nm to 2 nm.

FIG. 7 is a graph showing an example of the characteristics of themagnetic material on the underlying layer in the present embodiment.

In the graph of FIG. 7, the horizontal axis represents the thickness×ofthe buffer layer and the vertical axis represents the surface roughnessRq of the magnetic material. Hereinafter, the Ta layer of the bufferlayer will be referred to as a Ta buffer layer.

When the Ta buffer layer is provided between the Pt buffer layer and theHfB layer, the value of the surface roughness Rq of the magneticmaterial (e.g. SAF structure) is smaller than a comparative value V4even though the Ta buffer layer is formed to the thickness of 2 nm.

FIG. 8 is a graph showing an example of the characteristics of themagnetic material on the underlying layer in the present embodiment.

In the graph of FIG. 8, the horizontal axis represents thethickness×[nm] of the Ta buffer layer and the vertical axis representsthe strength Hex [Oe] of an exchange coupling magnetic field of themagnetic material on the underlying layer.

Since, as shown in FIG. 8, the Ta buffer layer having a thickness of 0.5nm or more is provided between the Pt layer and the HfB layer, thestrength Hex of the exchange coupling magnetic field of the magneticmaterial on the Pt/Ta/HfB layer is not less than a comparative value V5.

FIG. 9 is a graph showing an example of the characteristics of the MTJelement in the present embodiment.

In the graph of FIG. 9, the horizontal axis represents thethickness×[nm] of the Ta buffer layer and the vertical axis representsthe tunnel magnetic resistance ratio (TMR ratio) of the magnetoresistiveeffect element (MTJ element).

Since, as shown in FIG. 9, the Ta buffer layer having a thickness of 0.5nm or more is provided between the Pt layer and the HfB layer, the TMRratio of the MTJ element is higher than a comparative value V6.

Therefore, when the Ta layer having a thickness of 0.5 nm or more isprovided in the underlying layer as in the present embodiment, themagnetoresistive effect element (magnetic layer) on the buffer layer canbe improved in its flatness, magnetic properties and TMR ratio.

Based on the experimental results of FIGS. 7 through 9, the thickness ofthe Ta layer as the first buffer layer 191 can be set to 0.5 nm or more,preferably 2.0 nm or less. For example, the thickness of the Ta layer isset in a range from 0.5 nm to 1.0 nm. For example, the thickness of thefirst buffer layer (Ta layer) 191 is not less than that of the secondbuffer layer 192.

Note that the thickness of the first buffer layer 191 is not limited tothe examples of FIGS. 7 through 9 but may be larger than 2.0 nm inaccordance with the material for use. For example, the thickness of thefirst buffer layer 191 may be equal to or smaller than that of thesecond buffer layer (crystal layer) 192.

As shown in FIGS. 3 through 9 described above, in the presentembodiment, a magnetic material (e.g. SAF structure) is provided on theunderlying layer having a stack structure including an amorphous layerand a buffer layer, with the result that the magnetic material and theMTJ element are improved in their characteristics.

(d) Summary

In the magnetoresistive effect element (e.g. the MTJ element) as amagnetic device of the present embodiment, a magnetic materialconstituting the element is provided on the underlying layer. Theunderlying layer has a stack structure of an amorphous layer and abuffer layer. The buffer layer is, for example, a crystal layer.

The amorphous layer is provided between the buffer layer and thesubstrate. The buffer layer is provided between the magnetic materialand the amorphous layer.

In the present embodiment, the amorphous layer having substantially nocrystallinity can prevent the crystal properties (e.g., a crystaldefect, orientation of crystal, and a lattice mismatch) of a layer (e.g.an electrode, a contact plug and a substrate) under the amorphous layerfrom being propagated to a layer (e.g. a buffer layer and a magneticmaterial) above the amorphous layer.

For example, the amorphous layer has a relatively flat surface.

In the present embodiment, the buffer layer has a relatively flatsurface (top surface) in accordance with the flatness of the amorphouslayer. The buffer layer also has relatively good crystallinity accordingto the flat amorphous layer. In the present embodiment, therefore, thebuffer layer depends upon the crystallinity of the buffer layer and canpromote the crystal growth of the magnetic material provided on thebuffer layer. Thus, the magnetic material formed on the surface of thebuffer layer has relatively good crystallinity. As a result, themagnetic properties of the magnetic material are improved in the presentembodiment.

For example, when the shift cancellation layer is provided closer to thesubstrate than the storage layer and the reference layer as in theexample of FIG. 2, the characteristics of the shift cancellation layermay have a significant effect on the characteristics of themagnetoresistive effect element. The present embodiment can improve thecharacteristics of the magnetic layer used in the shift cancellationlayer.

As described above, the magnetoresistive effect element of the presentembodiment can improve the robustness against substrate types by thestack structure of the amorphous layer and the buffer layer (crystallayer).

Therefore, the magnetoresistive effect element of the present embodimentcan improve in its characteristics (e.g. TMR ratio).

As described above, the magnetic device (magnetoresistive effectelement) of the present embodiment can improve in its characteristics.

(2) Modification

A modification to the magnetoresistive effect element of the presentembodiment will be described with reference to FIG. 10.

FIG. 10 is a sectional view showing a modification to the magneticdevice (e.g. MTJ element) of the present embodiment.

As shown in FIG. 10, an MTJ element 400 of the modification includes noshift cancellation layer.

In the modification, the underlying layer 19 includes a first bufferlayer (crystal layer) 191, a second buffer layer (crystal Layer) 192 anda spacer layer (amorphous layer) 199.

Thus, the MTJ element 400 (reference layer 111) is improved in itsflatness and magnetic properties.

As a result, the MTJ element of the modification is improved in itscharacteristics.

Note that the order of lamination of the reference layer 111 and thestorage layer 12 in. the stack 10 may be opposite to that in theexamples shown in FIGS. 2 through 10. In this case, the storage layer 12is provided on the underlying later 19. The reference layer 111 isprovided above the storage layer 12 in the Z direction with the tunnelbarrier layer 13 therebetween. If the MTJ element 400 has an SAFstructure, a shift cancellation layer and a metal layer is providedbetween the reference layer and the upper electrode.

(3) Application Example

An application example of the magnetic device of the embodiment will bedescribed with reference to FIGS. 11 through 13.

FIG. 11 is a diagram illustrating an application example of the magneticdevice of the present embodiment.

The magnetic device (e.g. MTJ Element) of the present embodiment isapplied to a memory device.

As shown in FIG. 11, a memory device 1 including the magnetic device ofthe present embodiment is electrically connected to, for example, anexternal device such as a controller, a processor and a host device.

The memory device 1 receives a command CMD, an address ADR, input dataDIN and various control signals CNT from the external device. The memorydevice 1 transmits output data DOUT to the external device.

As shown in FIG. 11, the memory device 1 includes at least a memory cellarray 100, a row decoder 120, a word line driver (row control circuit)121, a column decoder 122, a bit line driver (column control circuit)123, a switch circuit 124, a write circuit (write control circuit) 125,a read circuit (read control circuit) 126 and a sequencer 127.

The memory cell array 100 includes a plurality of memory cells MC.

The row decoder 120 decodes a row address included in the address ADR.

Based on the decoding result of the row address, the word line driver121 selects a row (e.g. a word line) of the memory cell array 100. Theword line driver 121 can apply a predetermined voltage to the word line.

The column decoder 122 decodes a column address included in the addressADR.

Based on the decoding result of the column address, the bit line driver123 selects a column (e.g. a bit line) of the memory cell array 100. Thebit line driver 123 is connected to the memory cell array 100 via theswitch circuit 124. The bit line driver 123 can apply a predeterminedvoltage to the bit line.

The switch circuit 124 connects one of the write circuit 125 and readcircuit 126 to the memory cell array 100 and the bit line driver 123.Thus, the MRAM 1 performs an operation corresponding to the command.

During write operation, the write circuit 125 supplies various voltagesand/or currents for writing data to a memory cell selected based on theaddress ADR. For example, the data DIN is supplied to the write circuit124 as data to be written to the memory cell array 100. Thus, the writecircuit 125 writes the data DIN to the memory cell MC. the write circuit125 includes a write driver/sinker.

During read operation, the read circuit 126 supplies various voltagesand/or currents for reading data to a memory cell selected based on theaddress ADR. Accordingly, data is read from the memory cell MC.

The read circuit 126 outputs the data read from the memory cell array100, to the outside of the memory device 1 as output data DOUT.

The read circuit 126 includes a read driver, a sense amplifier circuitand the like.

The sequencer 127 receives the command CMD and various control signalsCNT. In response to the command CMD and control signals CNT, thesequencer 127 controls the operations of the circuits 120 to 126 in thememory device 1. The sequencer 127 can transmit the control signals CNTto an external device in accordance with the operating status of theinterior of the memory device 1.

For example, the sequencer 127 holds various items of information aboutthe write and read operations as setting information.

Note that different signals CMD, CNT, ADR, DIN and ROUT may be suppliedto a predetermined circuit in the memory device 1 via an interfacecircuit provided separately from the chip (package) of the memory device1 and may be supplied to the circuits 120 to 127 from an input/outputcircuit (not shown) in the memory device 1.

For example, in the present embodiment, the memory device 1 is amagnetic memory. In the magnetic memory (e.g. MRAM), themagnetoresistive effect element as the magnetic device of the presentembodiment is used in a memory element in the memory cell MC.

<Internal Configuration of Memory Cell Array>

FIG. 12 is an equivalent circuit diagram showing an example of theinternal configuration of the memory cell array of the MRAM according tothe present embodiment.

As shown in FIG. 12, a plurality of (n) word lines WL (WL<0>, WL<1>,WL<n−1>) are provided in the memory cell array 100. A plurality of (m)bit lines BL (BL<0>, BL<1>, BL<m−1>) and a plurality of (m) bit linesbBL (bBL<0>, bBL<1>, . . . , bBL<m−1>) are provided in the memory cellarray 100. One bit line BL and one bit line bBL constitute a bit linepair. For clarification of the description, the bit lines bBL may bereferred to as source lines.

The memory cells MC are arranged in matrix in the memory cell array 100.

The memory cells MC arranged in the D1 direction (row direction) areconnected to a common word line WL. The word line WL is connected to theword line driver 121. The word line driver 121 controls the potential ofthe word line WL based on a row address. Thus, the word line WL (row)represented by the row address is selected and activated.

The memory cells MC arranged in the D2 direction (column direction) areconnected in common to two bit lines BL and bBL belonging to one bitline pair. The bit lines BL and bBL are connected to the bit line driver123 through the switch circuit 124.

The switch circuit 124 connects the bit lines BL and bBL correspondingto a column address to the bit line driver 123. The bit line driver 123controls the potentials of the bit lines BL and bBL. Thus, the bit lineBL and bBL (column) represented by the column address are selected andactivated.

The switch circuit 124 connects the selected bit lines BL and bBL to thewrite circuit 125 or the read circuit 126 in accordance with theoperation requested by the memory cell MC.

For example, each of the memory cells MC includes a singlemagnetoresistive effect element 400 and a single cell transistor 600.

One end of the magnetoresistive effect element 400 is connected to thebit line BL. The other end of the magnetoresistive effect element 400 isconnected to one end (one of the source/drain) of the cell transistor600. The other end (the other of the source/drain) of the celltransistor 600 is connected to the bit line bBL. The word line WL isconnected to the gate of the cell transistor 600.

The memory cell MC may include two or more magnetoresistive effectelements 400 and may include two or more cell transistors 600.

The memory cell array 100 may have a configuration of a hierarchical bitline system. In this case, a plurality of global bit lines are providedin the memory cell array 100. Each bit line BL is connected to oneglobal bit line through the corresponding switch element. Each sourceline bBL is connected to the other global bit line through thecorresponding switch element. The global bit lines are connected to thewrite circuit 125 and the read circuit 126 through the switch circuit124.

The magnetoresistance effect element 400 functions as a memory element.The cell transistor 600 functions as a switching element of the memorycell MC.

For example, when the memory cell MC stores one-bit data (“0” data or“1” data), first data (e.g. “0” data) is associated with the MTJ element400 in a state having a first resistance value R1 (first resistancestate). Second data (e.g. “1” data) is associated with the MTJ element400 in a state having a second resistance value R2 (second resistancestate).

The resistance state (magnetization alignment) of the magnetoresistiveeffect element 400 varies with the supply of voltage or current of acertain magnitude to the magnetoresistive effect element 400.Accordingly, the magnetoresistive effect element 400 can be placed intoa plurality of resistance states (resistance values). Data of one ormore bits is associated with the resistance states of themagnetoresistive effect element 400. Thus, the magnetoresistive effectelement 400 is used as a memory element.

Incidentally, in the present embodiment, a well-known data writeoperation (data write using, e.g. a magnetic field write method, a spintransfer torque (STT) method and/or a spin orbit torque (SOT) method)and a well-known data read operation (data read using, e.g. a DC method,a reference cell method and/or a self-reference method) canappropriately be applied to the operation of the MRAM including themagnetoresistive effect element 400. In this embodiment, therefore, thedescription of the operation of the MRAM including the MTJ element 400of the present embodiment will be omitted.

<Configuration Example of Memory Cell>

FIG. 13 is a sectional view showing a configuration example of thememory cell of the MRAM according to the present embodiment.

As shown in FIG. 13, the memory cell MC is provided on the semiconductorsubstrate 80.

The cell transistor 600 is a transistor of any type. For example, thecell transistor 600 is an electric field effect transistor with a planarstructure, an electric field effect transistor with a three-dimensionalstructure such as FinFET, or an electric field effect transistor with anembedded gate structure. Hereinafter, a cell transistor with a planarstructure will be exemplified.

The cell transistor 600 is provided in an active region (semiconductorregion) AA of the semiconductor substrate 80.

In the cell transistor 600, a gate electrode 61 is provided above theactive region AA via a gate insulating film 62 therebetween. The gateelectrode 61 extends in the depth direction (or the front direction) ofFIG. 3. The gate electrode 61 functions as a word line WL.

The source/drain regions 63A and 63B of the cell transistor 600 areprovided in the active region AA.

A contact plug 55 is provided on the source/drain region 63B. Aninterconnect (metal layer) 56 serving as a bit line bBL is provided onthe contact plug 55. The contact plug 50 is provided on the source/drainregion 63A.

The magnetoresistive effect element 400 is provided on the contact plug50 and an interlayer insulating film 81. The magnetoresistive effectelement 400 is provided in the interlayer insulating film 82.

The magnetoresistive effect element 400 of the present embodimentincludes the stack 10 and the underlying layer 19 between the twoelectrodes 31 and 31. The stack 10 is a multilayer film having amagnetic tunnel junction.

The electrode 30 is provided on the contact plug 50. The electrode 31 isprovided above the electrode 30 with the stack 10 and the underlyinglayer 19 therebetween. A via plug 51 is provided on the electrode 31. Aninterconnect (metal layer) 52 serving as a bit line BL is provided onthe via plug 51 and the interlayer insulating film 82. A conductivelayer (e.g. a metal layer) may be provided between the electrode 30 andthe contact plug 50.

For example, an insulating film (also referred to as a protective filmand a sidewall insulating film) 20 covers the side of the MTJ element400. The protective film 20 is provided between the interlayerinsulating film 82 and tunnel junction 10. The protective film 20 may beprovided between each of the electrodes 30 and 31 and the interlayerinsulating film 82.

The material of the protective film 20 is selected from silicon nitride,aluminum nitride, aluminum oxide and the like. The protective film 20may be a single-layer film and a multilayer film.

The protective film 20 need not be formed. The shape of the protectivefilm 20 shown in FIG. 13 can be adjusted as appropriate.

Note that FIG. 13 simply shows a configuration of the magnetic deviceaccording to the present embodiment. FIG. 13 also simply shows the stack10 and the underlying layer (buffer layer and amorphous layer) 19. Inthe present embodiment, the configurations of the memory cell array andthe memory cell are not limited to the examples shown in FIGS. 12 and13.

As described above, in the present embodiment, the layer 19 including anamorphous layer and a buffer layer can improve the properties (e.g.magnetic properties) of the SAF structure including a reference layerand a shift cancellation layer.

Therefore, the magnetoresistive effect element of the present embodimentcan improve element characteristics.

Accordingly, the memory device including the magnetoresistive element ofthe present embodiment can improve in its characteristics.

(Others)

In the foregoing embodiment, the magnetic device may be an MTJ elementof an in-plane magnetization type. In this MTJ element, themagnetization of the storage layer 12, reference layer 111 and shiftcancellation layer 115 is directed to a direction perpendicular to thestack direction of the layers 12, 111 and 115. The easy axis ofmagnetization of the layers 12, 111 and 115 is parallel to the surface(X-Y plane) of the magnetic layer 12.

In the foregoing embodiment, a three-terminal type field effecttransistor is provided as a switching element (selector) of the memorycell. As the switching element, for example, a two-terminal typeswitching element may be used. For example, when a voltage to be appliedbetween two terminals is not higher than a threshold voltage, theswitching element is brought into a high-resistance state, such as anelectrically nonconductive state. When the voltage is not lower than thethreshold voltage, the state of the switching element is changed to alow-resistance state, such as an electrically conductive state. Theswitching element may have this function irrespective of the polarity ofthe voltage. The switching element may include at least one or moretypes of chalcogen elements selected from the group consisting of, e.g.tellurium (Te), selenium (Se) and sulfur (S). Alternatively, theswitching element may include, for example, chalcogenide that is acompound including the above chalcogen elements. The switching elementmay also include at least one or more types of elements selected fromthe group consisting of boron (B), aluminum (Al), gallium (Ga), indium(In), carbon (C), silicon (Si), germanium (Ge), tin (Sn), arsenic (As),phosphorus (P) and antimony (Sb).

The two-terminal type switching element described above is connected tothe magnetoresistive effect element via one or more conductive layers.

The above-described embodiment is directed to an example of applying themagnetic device (magnetoresistive effect element) of the presentembodiment to the MRAM. However, the magnetic device of the presentembodiment may be applied to a magnetic memory other than the MRAM. Themagnetic device of the present embodiment may also be applied to adevice (a magnetic head and/or a magnetic sensor) other than the memorydevice.

In the magnetic device (magnetoresistive element) of the presentembodiment, a buffer layer (crystal layer) having a single-layerstructure may also be provided between the magnetic layer and the spacerlayer (amorphous layer). In this case, for example, no second bufferlayer is provided between the first buffer layer and the spacer layer.In addition, a buffer layer having a three-layer structure may beprovided between the magnetic layer and the spacer layer.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A magnetic device comprising: a first magneticmaterial provided above a substrate; a second magnetic material providedbetween the substrate and the first magnetic material; a nonmagneticmaterial provided between the first magnetic material and the secondmagnetic material; a first layer provided between the substrate and thesecond magnetic material and including an amorphous layer; and a secondlayer provided between the amorphous layer and the second magneticmaterial and including a crystal layer.
 2. The magnetic device accordingto claim 1, wherein the second magnetic material includes a firstmagnetic layer, a second magnetic layer between the first magnetic layerand the second layer, and a nonmagnetic layer between the first magneticlayer and the second magnetic layer.
 3. The magnetic device according toclaim 1, wherein the second magnetic material has an SAF structure. 4.The magnetic device according to claim 1, wherein the amorphous layerincludes a boride layer.
 5. The magnetic device according to claim 1,wherein the crystal layer includes one of ruthenium, rhodium, palladium,osmium, iridium, platinum.
 6. The magnetic device according to claim 1,wherein the crystal layer is a stack of tantalum and one of ruthenium,rhodium, palladium, osmium, iridium, platinum.
 7. The magnetic deviceaccording to claim 1, wherein a thickness of the amorphous layer isequal to or thicker than a thickness of the crystal layer.
 8. Themagnetic device according to claim 1, wherein a thickness of theamorphous layer is 0.5 nm or more.
 9. The magnetic device according toclaim 1, wherein a thickness of the crystal layer is 0.5 nm or more and2 nm or less.
 10. A memory device comprising: a memory cell including amagnetic device, the magnetic device including: a first magneticmaterial provided above a substrate; a second magnetic material providedbetween the substrate and the first magnetic material; a nonmagneticmaterial provided between the first magnetic material and the secondmagnetic material; a first layer provided between the substrate and thesecond magnetic material and including an amorphous layer; and a secondlayer provided between the amorphous layer and the second magneticmaterial and including a crystal layer; and a control circuit configuredto control a operation of the memory cell and provided on the substrate.11. The memory device according to claim 10, wherein the second magneticmaterial includes a first magnetic layer, a second magnetic layerbetween the first magnetic layer and the second layer, and a nonmagneticlayer between the first magnetic layer and the second magnetic layer.12. The memory device according to claim 10, wherein the second magneticmaterial has an SAF structure.
 13. The memory device according to claim10, wherein the amorphous layer includes a boride layer.
 14. The memorydevice according to claim 10, wherein the crystal layer includes one ofruthenium, rhodium, palladium, osmium, iridium, platinum.
 15. The memorydevice according to claim 10, wherein the crystal layer is a stack oftantalum and one of ruthenium, rhodium, palladium, osmium, iridium,platinum.
 16. The memory device according to claim 10, wherein athickness of the amorphous layer is equal to or thicker than a thicknessof the crystal layer.
 17. The memory device according to claim 10,wherein a thickness of the amorphous layer is 0.5 nm or more.
 18. Thememory device according to claim 10, wherein a thickness of the crystallayer is 0.5 nm or more and 2 nm or less.